The present invention relates, in general, to a crane installation, and more particularly to a container crane of a type having a hoist mechanism with one or more motors for lifting and lowering a suspended load, and a control unit for controlling operation of the hoist mechanism.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Crane installations of this type are generally used for loading and unloading of container ships. The crane typically includes a trolley which travels along a boom spanning over the ship and a hoist mechanism attached to the trolley. Suspended from the hoist mechanism via ropes is a load-carrying frame, normally a container spreader which grabs a container for loading onto the ship or unloading from the ship. The hoist mechanism normally includes one or more motors for driving one or more drums, used for winding the ropes, to thereby lift or lower a load. This type of crane installation is referred to also as single-trolley container crane. Another construction involves the configuration of a two-trolley container crane installation which has two separate trolleys, each having its own hoist mechanism. One trolley, referred to as primary trolley, assumes the actual loading and unloading of the ship for placing a container from the ship on a placement area on the side of the crane or for transferring a container from the crane-side placement area to the ship. The other trolley is referred to as gantry trolley and transports the container from the placement area to a crane-distal transport vehicle, e.g. a driverless terminal vehicle or a railway car, or removes the container from the transport vehicle for transfer to the placement area, oftentimes also called reception platform.
These types of container crane installations suffer shortcomings when the loads are bulky or when loads of unknown weight need to be transshipped. These situations oftentimes subject the hoist mechanism and motors to extreme stress that frequently results in damage. Also in the event of an uneven load distribution, the boom may be exposed to inadmissible forces that in extreme cases can impact the static of the crane.
It would therefore be desirable and advantageous to provide an improved crane installation to obviate prior art shortcomings.